The present invention relates to a single-control thermostatic cartridge.
In the sanitation field, a cartridge is a device making it possible to regulate hot and cold fluids to be mixed, in particular hot water and cold water. In a thermostatic cartridge, the regulation is obtained using a thermostatic element that comprises a first part that is normally stationary relative to a hollow base of the cartridge on the one hand, and a second part that is movable along an axis relative to the first part under the action of the expansion of a thermo-expansive material of the thermostatic element and that is secured to a regulating slide valve on the other hand. This slide valve is movable along the axis inside the base of the cartridge, so as to inversely vary the flow sections of the hot and cold fluids, supplying the base through a first of its axial sides, in order to mix those two fluids in variable proportions to obtain, downstream from the slide valve, a fluid, called “blended fluid”, “mixture” or “mixed fluid”, that flows along a heat-sensitive region of the thermostatic element and leaves the base through its second axial side. By modifying the position of the first part of the thermostatic element relative to the base, using an ad hoc control mechanism, the thermostatic regulation temperature is set, i.e., the equilibrium temperature around which the temperature of the mixture is regulated. This type of cartridge incorporates discs or functionally similar elements to control the cold and hot fluid flow rates, sent toward the slide valve: these discs are mounted inside a cover fixed to the base, while being arranged overhanging the first axial side of the base, and are supplied with the cold and hot fluids via flow channels of those fluids extending from the second axial side of the base to the first axial side of the base. It is even possible to have only a single handle, carried movably by the aforementioned cover, to control both these adjusting discs for the flow rate and the aforementioned control mechanism: in that case, the thermostatic cartridge is described as single-control. WO-A-96/26475 and WO-A-2010/072966 provide examples of this.
In the case of WO-A-2010/072966, the control mechanism includes a control rod, which acts axially on the thermostatic element to modify its position along the axis relative to the base and on which a control screw acts axially, locked in rotation around the axis and screwed in a control nut connected to the handle in rotation: in other words, rotating the handle around the axis actuates a screw-nut system, formed by the aforementioned control screw and control nut, which translates the thermostatic element axially in one direction, with the understanding that, in the opposite direction, the thermostatic element is kept bearing axially against the control screw under the action of a return spring. The cartridge of WO-A-2010/072966 further incorporates an overtravel spring, which is stiffer than the return spring and which is designed to be compressed only during a deployment of the thermostatic element such that the slide valve abuts axially against a resistant surface of the base, in order to avoid damaging the slide valve and/or that of the thermostatic element. This overtravel spring is typically compressed when the supply of the cartridge with cold fluid is cut, in order to provide the user with protection against being burned by the hot water. The overtravel spring is inserted axially between the control rod and the control screw, while being housed inside this control screw to gain compactness.
In the case of WO-A-96/26475, a functionally similar overtravel spring is also provided, but while being axially inserted between a control rod and a compression plate of the spring, screwed, during the assembly of the cartridge, inside a control pin, which is mounted rotatably-translatably on the base by a threaded connection and that is connected in rotation around the axis of the handle. In other words, the control mechanism of WO-A-96/26475 is less sophisticated than that of WO-A-2010/072966. Furthermore, in one of the embodiments of WO-A-96/26475, it is provided to arrange the overtravel spring inside a fine adjustment bush, which is screwed inside the control pin: it then becomes possible, for a fixed position of the control pin, in other words, for a fixed position of the handle, to provide a fine adjustment of the position of the bush, and therefore of the overtravel spring and the control rod, along the axis in order to modify the position of the thermostatic element along the axis accordingly. In this way, it will be understood that it is possible to provide a fine adjustment of the thermostatic regulation temperature controlled by the handle, at the end of manufacturing of the cartridge or during its installation. Thus, the fine adjustment bush of WO-A-96/26475 is of technical interest, but its screwing-unscrewing inside the pin is tedious and is presence is particularly cumbersome, since this bush takes on the entire overtravel spring.